In automotive vehicles, a wheel's travel pattern is controlled by its suspension geometry. The suspension layout employed to connect the individual wheels to the vehicle structure defines the suspension-linkage design. The linkage is pivotally connected through bushings to both the vehicle body and the wheel to allow the wheel to move vertically to compensate for irregularities in the road surface. The suspension design is determined by components, such as toe-in, defined as the angle between an axis extending parallel to the vehicle's longitudinal axis extending through the center pivot of the wheel and an axis through the center of the wheel. Toe-in compensates for forces exerted on the tire and keeps the wheels aligned preventing a condition known as dog tracking. Dog tracking is a condition where the rear wheels do not follow the front wheels preventing the vehicle from traveling squarely down the road.
Some automobiles do not have a wheel toe-in angle adjustment. The rear toe-in angle is set at the factory and built in during manufacturing. This is usually achieved by selecting a length for the suspension linkage and mounting the linkage through the bushings to the vehicle body and wheel. The bushings generally extend parallel to the vehicle centerline and have a central hole for a bolt for connection to the vehicle body and wheel. Each linkage extends transversely to the vehicle centerline so that each link pivots about the bushings. One problem that occurs in vehicles that lack rear toe-in angle adjustment is that if the wheels become misaligned due to, for instance, an automobile accident, there is no accurate way to realign the rear wheels. One attempt to correct this lack of adjustment feature was to provide special bushing kits to compensate for the misalignment. These special bushings have an off-center hole for the bolt which would replace the factory installed bushing connecting the linkage to the wheels. With these kits, one is only able to guess at the amount of misalignment and attempt to fit the offset bushing into the suspension to correct the misalignment. However, these kits are marginal at best and typically the wheels remain out of alignment.
Other vehicles do provide a mechanism for making a wheel toe-in adjustment. One such device is disclosed in U.S. Pat. No. 4,453,733 wherein a special swivel bearing is mounted to a torsion-proof arm and to a bracket secured to the vehicle body. A strut is connected at each end to the torsion-proof arm and to the bracket through ball and socket joints extending therebetween. Ball joint sockets are threaded into each end of the strut and provide a length-adjustment to change the toe-in angle of the wheel.
Another type of adjustment mechanism is disclosed in U.S. Pat. No. 5,027,275 which discloses a lateral link comprising an inner and outer lateral link member have a screw-threaded adjustment rod therebetween and a lock nut. The outer link is connected to a vehicle wheel. The toe-in angle is adjusted by loosening the lock nut and rotating the adjustment rod to shorten or lengthen the lateral link.
These devices are generally very expensive to manufacture, are time consuming to assemble and adjust, and are not adapted to be retrofit to existing automobile suspensions.